Available data indicate that sage grouse Centrocercus urophasianus have declined throughout their range. This species presently occurs in 11 U.S. States and in two Canadian provinces. In nine states having long-term data, breeding populations have declined by 17–47% ( = 33%) from the longterm average. Six states have long-term information on sage grouse production. In five of these states, production has declined by 10–51% ( = 25%) from the long-term average. Habitat deterioration, loss, and fragmentation have reduced the quantity and quality of nesting and early brood-rearing habitat causing population declines. Factors appearing to be largely responsible for the changes in habitats and, ultimately, sage grouse populations over wide areas of western North America are discussed, and hypotheses that could be tested to provide better insight into sage grouse population declines are suggested. Once these changes are better understood, conservation strategies that address protection and rehabilitation of sagebrush Artemisia spp. rangelands should be developed and implemented in each state and province to halt the decline of sage grouse and initiate recovery.